DE102006042886A1 - White, one-side matt, biaxially oriented polyester film, process for its preparation and its use - Google Patents

Abstract

The invention relates to white, biaxially oriented polyester films which have at least one polyester-containing base layer (B) and at least one matt cover layer (A), the cover layer (A) containing, in addition to the white pigment, further particles, preferably SiO <SUB> 2 </ SUB>, which has an average diameter of 2 to 10 microns, and wherein the cover layer (A) contains a polyester having isophthalic acid units. Optionally, the film is functionalized on at least one surface. These films are characterized in particular by a low gloss of the outer layer (A), a high degree of whiteness and high processing safety and are therefore suitable as flexible packaging films for use on high-speed packaging machines.

Description

The Invention relates to a white, one-side matt, coextruded, biaxially oriented polyester film, consisting of at least one white base layer (B) and at least one on this white Base layer (B) applied matte topcoat (A). The foil is characterized by a characteristic matt surface of the Cover layer (A) and high roughness. The film of the invention can over it Have at least one functionalized surface, whereby z. B. good adhesion achieved other polymer or metal layers or printing inks becomes. This is what this surface becomes coated with an adhesion-promoting layer in-line. The invention further relates to a process for producing the film and its Use.

The Packaging industry has a high demand for transparent, high-gloss Plastic films such. B. biaxially oriented polypropylene or biaxially oriented polyester films. There is also increasing Dimensions Need for such transparent films in which at least one Surface layer not high gloss is, but through a characteristic dull appearance characterized and thereby z. B. the packaging is a particularly attractive and thus gives a promotional effect.

typical Applications for white Biaxially oriented polyester films are lidding applications for "trays" and yoghurt pots. white Biaxially oriented polyester films are known in the art well known.

In the EP-A-0 347 646 describes a biaxially oriented polyester film having at least one outer layer A, which contains a filler in a concentration of 0.5 to 50%, wherein the diameter of this filler is in a certain ratio to the layer thickness of the outer layer A. Furthermore, the cover layer A has a certain thickness and a certain degree of crystallization, which is determined by means of Raman spectroscopy. Due to the topography of the outer layer A, the film is particularly suitable for magnetic recording tapes. About the achieved gloss of the top layer A is the font no information. One after the EP-A-0 347 646 (Example 1) produced film did not have the desired matte surface.

In the EP-A-0 053 498 describes a multilayer, biaxially oriented polyester film which has a transparent base layer (B) and on at least one side of this layer a matte appearing further layer (A). This matt-seeming layer consists essentially of a polyethylene terephthalate copolyester, the
H (-OCH ₂ CH ₂ -) _n OH units or
H (-OCH ₂ -CH ₂ -) _n-1 OC ₆ H ₄ -O- (CH ₂ -CH ₂ O-) _n-1 H units or
H (-OCH ₂ -CH ₂ -) _n-1 OC ₆ H ₄ -XC ₆ H ₄ -O- (CH ₂ -CH ₂ O-) _n-1 H units
(n is an integer from 2 to 140, X is -CH ₂ -, -C (CH ₃ ) ₂ - or -SO ₂ -) and inert inorganic particles having a mean diameter of 0.3 to 20 microns in one Concentration of 3 to 40%, based on the dull-seeming layer. The film is characterized by a high degree of matting (gloss less than 15) and, for certain applications, acceptable transparency (greater than 60%). A disadvantage of this film is that it can not be printed in the case of an ABA structure and, in the case of an AB structure, in particular can not be processed on high-speed machines. In addition, it is too transparent for many applications and has manufacturing defects.

Also are known in the art matte, milky-shining, biaxially oriented polyester films.

In the DE-A-23 53 347 describes a process for producing a mono- or multilayer, milky polyester film, which is characterized in that a mixture of particles of a linear polyester with 3 to 27 wt .-% of a homopolymer or copolymers of ethylene or propylene produces, the mixture as Film extruded, the film quenched and biaxially oriented by stretching in mutually perpendicular directions and heat-set the film. A disadvantage of the process is that the regenerate produced in the production of the film (essentially a mixture of polyester raw material and ethylene or propylene copolymer) can no longer be used again in film production, since otherwise the film turns yellow. The process is therefore uneconomical, and produced with regenerated, yellowish film could not prevail on the market. When the concentration of the copolymer in the polyester is increased, the film generally loses its milky character and turns white. Whiteness is not enough for many applications. The yellowing of the film has a negative effect on the printed image and is therefore undesirable.

In the U.S. Patent 3,154,461 For example, a biaxially oriented thermoplastic film (eg, polyethylene terephthalate, polypropylene) having a matte surface is claimed, the incompressible particles (eg, calcium carbonate, silicon dioxide) having a size of 0.3 to 20 μm and a concentration of 1 contains up to 25%. For many transparent applications, however, this film is too opaque and too transparent for many white applications and the whiteness too low.

The EP-B-0 605 130 describes a multilayer, coextruded composite film having a thickness in the range of 30 to 400 microns. The film comprises a cloudy crystalline first polyester layer substantially impermeable to visible light, a density greater than 1.30 g / cm ³ , a thickness greater than or equal to 25 μm and a deformation index greater than or equal to 2, 5%. The deformation index is measured at a temperature of 200 ° C and under a pressure of 2 MPa. In addition, the film comprises a transparent, crystalline second polyester layer, which is "substantially permeable to visible light" and has a transmission optical density (TOD) of 0.005 to 0.2. Furthermore, in the context of the invention, a transparency of this layer is still present if less than 2% particles are present in it, which have a particle size of 0.1 to 10 microns. The film is characterized by a good opacity, but it has deficiencies in their production (no optimal role presentation), in their processing to cover and in particular in the optical properties.

The EP-A-1 176 004 describes a white biaxially oriented, usually monolayer polyester film with a base layer (B), which is due to their special mechanical properties very well as a lidding film, in particular as a lidding film for yogurt cups, is suitable. The film is characterized in that the R value is less than or equal to 45 N / mm ² and the e _max ratio is less than or equal to 2.5. By complying with these values, the film is less susceptible to delamination and exhibits good peel performance from the cup. The film is still characterized by good opacity, but it still has deficiencies in their production (no optimal role presentation) and in the optical properties.

task Therefore, it was the object of the present invention to provide a white at least to provide one-sided matt, biaxially oriented polyester film, the disadvantages of the mentioned films from the prior art does not have and in particular by a high degree of matt - at the same time low transparency - and high whiteness, a very good manufacturability and a very good processability distinguished. In the production of the film should continue to be guaranteed be that incurred in the film production waste material as Regenerat can be returned to the manufacturing process without that while the physical and optical properties of the film worth mentioning be negatively influenced.

The object is achieved by a white biaxially oriented polyester film which has at least one white base layer (B) and at least one matte outer layer (A), the outer layer (A) containing, in addition to the white pigment, further particles which preferably have a mean particle diameter d ₅₀ of 2 to 10 microns and are preferably contained in a concentration of 1 to 7 wt .-%. The cover layer (A) contains a polyester having 4 to 30 mol% of isophthalic acid units based on the total amount of acid of the polyester in this layer. The white pigment is contained in a concentration of 2 to 15 wt .-% (wt .-% of information based on the weight of the outer layer (A)). Optionally, at least one of the two film surfaces carries a function-promoting coating or is function-mediated. This coating is preferably applied to the film as an aqueous dispersion. In a preferred embodiment, the function-promoting coating is applied to the matte top layer (A).

According to the invention At least two layers of film and then includes as layers Base layer (B) and the matte top layer (A). In a preferred embodiment the invention, the film is constructed in three layers and has one side of the layer (B) (= base layer), the cover layer according to the invention (A) and on the other side of the layer (B) another layer (C) on. In this case, the two layers (A) and (C) form the outer layers (A) and (C). The film of the invention has moreover optionally on at least one film surface a function-promoting Coating on, preferably as an aqueous dispersion on the film is applied.

Base layer (B)

The base layer (B) of the film preferably contains at least 80% by weight of thermoplastic polyester, in particular at least 90% by weight of thermoplastic polyester, based on the total weight of this layer. Suitable for this are z. Example, polyester from ethylene glycol and terephthalic acid (= polyethylene terephthalate, PET), from ethylene glycol and naphthalene-2,6-dicarboxylic acid (= polyethylene-2,6-naphthalate, PEN), from 1,4-bis-hydroxymethyl-cyclohexane and terephthalic acid = Poly (1,4-cyclohexanedimethylene terephthalate), PCDT] and ethylene glycol, naphthalene-2,6-dicarboxylic acid and biphenyl-4,4'-dicarboxylic acid (= polyethylene-2,6-naphthalate bibenzoate, PENBB). Particular preference is given to polyesters which consist of at least 90 mol%, in particular at least 95 mol%, of ethylene glycol and terephthalic acid units or of ethylene glycol and naphthalene-2,6-dicarboxylic acid units. In a most preferred embodiment, the base layer is polyethylene terephthalate homopolymer. The remaining monomer units are derived from other aliphatic, cycloaliphatic or aromatic diols or other dicarboxylic acids.

Suitable other aliphatic diols are, for example, diethylene glycol, triethylene glycol, aliphatic glycols of the general formula HO- (CH ₂ ) _n -OH, where n is an integer from 3 to 6 (propane-1,3-diol, butane-1,4-diol). diol, pentane-1,5-diol and hexane-1,6-diol) or branched aliphatic glycols having up to 6 carbon atoms. Of the cycloaliphatic diols, mention may be made of cyclohexanediols (in particular cyclohexane-1,4-diol).

The Preparation of the polyester can z. B. according to the known transesterification respectively. It is based on dicarboxylic acid esters and diols, the with the usual Transesterification catalysts such as zinc, calcium, lithium, magnesium and manganese salts are implemented. The intermediates will be then generally more common in the presence Polycondensation catalysts such as antimony trioxide or titanium salts polycondensed. The production can be just as good after the direct esterification process in the presence of polycondensation catalysts. there starting directly from the dicarboxylic acids and diols.

The Base layer (B) contains Furthermore a white pigment in a concentration of 3 to 15% by weight, preferably 4 to 14 wt .-% and particularly preferably from 5 to 13 wt .-%.

The by coextrusion on the base layer (B) applied matte topcoat (A) is preferably predominant built on the basis of polyester. According to the invention, the matt top layer (A) contains a polyester containing 4 to 30 mol% isophthalic acid, preferably 6 to 28 mol% isophthalic and more preferably 8 to 26 mol% of isophthalic acid on the total amount of acid of the polyester in this layer. The remaining monomer units come from other aliphatic, cycloaliphatic or aromatic dicarboxylic acids or Diols, as they can also occur in the base layer and have already been described there.

The matt cover layer (A) contains a white pigment in a concentration of 2 to 15 wt .-%, preferably from 3 to 14 wt .-% and particularly preferably from 4 to 13 wt .-%. Furthermore contains the cover layer (A) particles in a concentration of 1 to 7 Wt .-%, wherein these particles of white pigments different particles are.

The Raw materials for the outer layer (A) can be, for example, via copolymerization of the individual monomers or over Masterbatches of various individual polymers as a mixture or as Make a blend.

In a preferred embodiment of the invention the matt top layer (A) a copolyester consisting of terephthalate and isophthalate units and composed of ethylene glycol units is. The proportion of terephthalate units in this copolyester, based on the total amount of acid, is preferably 70 to 96 mol% and the corresponding proportion of isophthalate units 30 to 4 mol%. Particularly preferred among these are copolyesters, in which the proportion of terephthalate units 72 to 94 mol% and the corresponding proportion of isophthalate units 6 to 28 mol% is. Very preferred are those copolyesters in which the proportion of Terephthalate units 74 to 92 mol% and the corresponding proportion of isophthalate units is 6 to 26 mol%.

If be available for the remaining proportion of the polymers present in the outer layer (A) in principle used the same polymers as previously described for the base layer (B) were.

white pigment

To achieve the aforementioned properties, in particular the desired whiteness of the film, the necessary white pigments are incorporated in the base layer (B) and at least in a cover layer (A), but possibly also in other existing layers. In question come z. As titanium dioxide, barium sulfate, zinc sulfide or zinc oxide. Preferably, TiO _{2 is used} as the sole whitening pigment. It is added in the preferred embodiment as Extrusionsmaster batch the original raw material (polyester). Typical ranges for the TiO ₂ concentration in the extrusion masterbatch are 20 to 70% by weight. The titanium dioxide can be either rutile-type or anatase-type or a mixture of rutile and ana be tas type. Preferably, rutile type titanium dioxide is used in the base layer and in the overcoat layer. The particle size of the titanium dioxide is generally between 0.05 and 0.5 .mu.m, preferably between 0.1 and 0.3 .mu.m. The film gets a brilliant white appearance through the incorporated pigments in the intended concentrations.

Surprisingly has been shown to be when using the previously described Raw materials, especially in the use of isophthalic acid in the specified concentration, for the cover layer (A) a film with a particularly high roughness and low Shine gets.

• 1) Erfindungsgemäß enthält die matte Deckschicht (A) Partikel mit einem Partikeldurchmesser d₅₀ von 2,0 bis 10 μm. Es hat sich als besonders vorteilhaft erwiesen, Teilchen mit einem mittleren Partikeldurchmesser d₅₀ von 2,2 bis 9 μm, bevorzugt von 2,4 bis 8 μm und besonders bevorzugt von 2,6 bis 7 μm zu verwenden. Bei der Verwendung von Teilchen mit einem Durchmesser, der unterhalb 2,0 μm liegt, ist die Rauigkeit der Folie zu niedrig und der Glanz zu hoch. Teilchen mit einem Durchmesser größer als 10 μm verursachen in der Regel Filterprobleme.
• 2) Erfindungsgemäß enthält die Deckschicht (A) Partikel in einer Konzentration von 1 bis 7 Gew.-%, bezogen auf das Gesamtgewicht dieser Schicht. Bevorzugt beträgt die Konzentration der Partikel 1,5 bis 6,5 Gew.-% und besonders bevorzugt 2 bis 6 Gew.-%. Enthält die Deckschicht (A) der Folie dagegen Partikel in einer Konzentration von weniger als 1 Gew.-%, so ist der Mattgrad nicht ausreichend, der Glanz ist zu hoch. Enthält dagegen die Deckschicht (A) der Folie Partikel in einer Konzentration von mehr als 7 Gew.-%, so wird die homogene Einarbeitung der Partikel erschwert und kann zu unerwünschten Inhomogenitäten in der Oberfläche führen.

In order to achieve the desired mattness / desired degree of matting, the white outer layer (A) additionally contains, in addition to the white pigment, particles other than white pigments, which are characterized by the following set of preferred parameters:

• 1) According to the invention, the matte covering layer (A) contains particles having a particle diameter d ₅₀ of 2.0 to 10 μm. It has proved to be particularly advantageous to use particles having a mean particle diameter d ₅₀ of 2.2 to 9 microns, preferably from 2.4 to 8 microns and more preferably from 2.6 to 7 microns. When using particles with a diameter below 2.0 μm, the roughness of the film is too low and the gloss is too high. Particles with a diameter greater than 10 microns usually cause filter problems.
• 2) According to the invention, the outer layer (A) contains particles in a concentration of 1 to 7 wt .-%, based on the total weight of this layer. The concentration of the particles is preferably 1.5 to 6.5% by weight and more preferably 2 to 6% by weight. On the other hand, if the cover layer (A) of the film contains particles in a concentration of less than 1% by weight, the degree of matting is insufficient, the gloss is too high. If, in contrast, the outer layer (A) of the film contains particles in a concentration of more than 7% by weight, the homogeneous incorporation of the particles is made more difficult and can lead to undesirable inhomogeneities in the surface.

typical, favoring the degree of matting of the film and thus preferred particles are inorganic and / or organic Particles, for example calcium carbonate, amorphous silica, talc, Magnesium carbonate, barium carbonate, calcium sulfate, lithium phosphate, Calcium phosphate, magnesium phosphate, alumina, lithium fluoride, Calcium, barium, zinc or manganese salts of the dicarboxylic acids used, kaolin or crosslinked polymer particles, e.g. As polystyrene or acrylate particles.

Besides can also mixtures of two or more different particles or Mixtures of particles having the same chemical composition, but different particle size can be selected. The particles can be the Polymers of the individual layers of the film in the respectively advantageous Concentrations, e.g. B. as a glycolic dispersion during the Polycondensation or over Masterbatches in the extrusion, to be added.

Preferred particles are synthetically produced SiO ₂ particles (in colloidal form). These particles are very well integrated into the polymer matrix. Manufacturers of such particles are z. The companies Grace (US), Fuji (JP), Degussa (DE) or Ineos (GB).

Around to the desired whiteness (> 75, preferably> 80, more preferably> 85) and to the desired low transparency (<50%, preferably <45%, more preferably <40%) To reach the film, the base layer (B) should be highly filled.

Lies the whiteness below 75, the slide does not appear white enough to the observer. As a result, the film becomes less effective and the printed image appears not so brilliant anymore.

Lies the transparency over 50%, the film appears milky white. The food under the film can be seen. The permeability of light has a significant impact on the durability of certain Food. Less translucent food packaging often have a much higher shelf life in photosensitive foods.

In a preferred embodiment, to further increase the whiteness, suitable optical brighteners may be added to the base layer and / or the other layers. Suitable optical brighteners are, for example Hostalux KS ^® from Clariant ^® or Eastobrite OB-1 from Eastman.

• 1) Die Rauigkeit der matten Seite der Folie, ausgedrückt durch ihren R_a-Wert, liegt im Bereich von 150 bis 1000 nm, bevorzugt von 175 bis 950 nm, besonders bevorzugt von 200 bis 900 nm. Kleinere Werte als 150 nm haben negative Auswirkungen auf den Mattheitsgrad der Oberfläche, größere Werte als 1000 nm beeinträchtigen die optischen Eigenschaften der Folie.
• 2) Die Oberfläche der matten Seite der Folie weist > 100 bis < 1500 Erhebungen pro mm² auf, die größer als 1,5 μm sind.

The matte topcoat (A) is further characterized in a preferred embodiment by the following set of parameters:

• 1) The roughness of the matte side of the film, expressed by its R _a value, is in the range from 150 to 1000 nm, preferably from 175 to 950 nm, more preferably from 200 to 900 nm. Smaller values than 150 nm have negative effects on the mattness of the surface, greater than 1000 nm affect the optical properties of the film.
• 2) The surface of the matte side of the film has> 100 to <1500 bumps per mm ² , which are larger than 1.5 microns.

The Base layer (B) may also additionally conventional additives such as Stabilizers and / or particles (= filler) included. As stabilizers For example, phosphorus compounds such as phosphoric acid or organophosphate used.

typical Particles (filler) for the Base layer (B) are the for the cover layer (s) specified inorganic and / or organic Particles, for example calcium carbonate, amorphous silica, talc, Magnesium carbonate, barium carbonate, calcium sulfate, lithium phosphate, Calcium phosphate, magnesium phosphate, alumina, lithium fluoride, Calcium, barium, zinc or manganese salts of the dicarboxylic acids used, carbon black, kaolin or crosslinked polystyrene or acrylate particles.

In In the preferred form of use, the film consists of three layers, the base layer (B) and applied on both sides of this base layer Cover layers (A) and (C), wherein the cover layers (A) and (C) are the same or may be different. The cover layer (C) contains prefers the for the base layer (B) described polymers. In particular, the layer contains (C) prefers the above-mentioned fillers (particles) to the processing behavior the film continues to improve.

Between the base layer (B) and the outer layers (A) and / or (C) may be optionally one or more intermediate layers are still. these can turn from the for consist of the base layer (B) described polymers. In a particularly preferred embodiment the intermediate layer consists of that used for the base layer (B) Polyester. The intermediate layer can also be the usual described Contain additives. The thickness of the intermediate layer is generally greater than 0.3 μm and is preferably in the range of 0.5 to 15 .mu.m, in particular in the range of 1.0 to 10 μm, more preferably in the range of 1.0 to 5 microns.

at the particularly advantageous three-layer embodiment of the film according to the invention the thickness of the outer layers (A) and (C) is generally in the Range of 0.1 to 5.0 μm, preferably in the range of 0.3 to 4.5 .mu.m and more preferably in Range of 0.5 to 4.0 μm, wherein the matte top layer (A) and the top layer (C) are the same or can be different in thickness.

The Total thickness of the polyester film according to the invention can vary within wide limits. It is usually in the range of 5 to 500 μm, in particular from 8 to 400 μm, preferably from 10 to 300 microns.

Summarized the film of the invention is characterized in particular by a low gloss of the film surface (A), by a comparatively high roughness and a low transparency out. Furthermore it has a good wrapping and processing behavior.

The inventive film is suitable as a packaging material for food and beverages, in particular as a cover foil for Food containers such as B. yogurt cups. The film is also excellent for packaging moisture and / or air sensitive food and stimulants which are also contained in such cups can.

Of the Gloss of the film surface (A), measured at an angle of incidence of 60 °, is lower than 50. In one preferred embodiment is the gloss of this page is less than 45 and in a particularly preferred embodiment less than 40. The whiteness the film, measured by Berger, is greater than 75, preferably greater than 80 and more preferably greater than 85th

The The invention also relates to a process for the preparation of the polyester film according to the invention according to the coextrusion process known from the literature.

In the context of this process, the procedure is such that the melts corresponding to the individual layers (A), (B) and optionally (C) of the film are coextruded through a flat die and shaped into melt films, the film thus obtained being solidified on one or more rolls / n abge The film is then biaxially stretched (oriented), the biaxially stretched film is heat-set and, if appropriate, corona or flame-treated on the surface layer intended for the treatment.

The biaxial stretching (orientation) generally coincides following, the successive biaxial stretching, at first along (in Machine direction) and then across (perpendicular to the machine direction) is stretched, is preferred.

First, as usual in the coextrusion process, the polymer or the polymer mixtures for the individual layers in each compressed an extruder and liquefied, where appropriate as additives provided additives already in the polymer or in the polymer mixture may be included. These additives are preferred in the form of masterbatches to the starting polymer added. The melts are then pressed simultaneously through a flat die (slot die), and the extruded, multi-layered melt is on or withdrawn several take-off rolls, wherein the melt cools and solidifies into a prefilm.

The Biaxial stretching is generally performed sequentially. there Preferably, the prefilm is first longitudinally (i.e., in the machine direction = MD direction) and then in the transverse direction (i.e., perpendicular to the machine direction = TD direction). this leads to to a spatial Orientation (orientation) of the polymer chains. The stretching in the longitudinal direction let yourself with the help of two different according to the desired stretch ratio fast rotating rollers. Used for cross stretching you generally have a corresponding clip frame in which the film on both edges clamped and then at elevated Temperature is drawn to both sides.

The Temperature at which the stretching is carried out can be done in a relative huge Range vary and depends on the desired properties of the film. In general, the longitudinal stretching is at a temperature in the range of 80 to 130 ° C and the transverse extent in the range from 80 to 150 ° C carried out. The longitudinal stretching ratio is generally in the range of 2.5: 1 to 5: 1, preferably from 3: 1 to 4.5: 1. The Transverse stretching ratio is generally in the range of 3.0: 1 to 5.0: 1, preferably 3.5: 1 to 4.5: 1.

at the subsequent heat setting is the film over a Duration of about 0.1 to 10 seconds at a temperature of about 180 up to 250 ° C held. Subsequently The film is in the usual Wrapped up way.

As already mentioned at the beginning At least one film surface can be functionally coated and / or treated. The contact angle of this coated / treated surface to water is ≤ 64 °, preferably ≤ 62 ° and especially preferably ≤ 60 °. This coated / treated surface has in particular an increased adhesiveness across from other materials.

This is achieved by a corona or flame treatment, which usually follows the thermosetting of the film. Likewise, the treatment at other locations in the film production process, for example, after the longitudinal stretching, take place. Alternatively or in addition to the surface treatment described above, the film may be coated on one (or both) surface (s) with a functional coating so that the coating on the finished film has a thickness of preferably 5 to 2000 nm, especially 20 to 500 nm and particularly preferably 30 to 200 nm. The coating is preferably applied in-line, ie during the film production process, expediently before the transverse extension. Particularly preferred is the application by means of the "reverse gravure-roll coating" process, in which the coating can be applied very homogeneously in layer thicknesses of up to 200 nm, likewise preferred is the application by the Meyer-Rod process, which allows larger coating thicknesses The coatings are preferably applied as solutions, suspensions or dispersions, particularly preferably as aqueous solution, suspension or dispersion, The coatings mentioned give the film surface an additional function, for example the film becomes sealable, printable, metallizable, sterilizable, antistatic, or, for example, they enhance the aroma barrier or allow adhesion to materials that would otherwise not adhere to the film surface Examples of fabrics / compositions that impart additional functionality are: acrylates, such as those described in U.S. Pat WO 94/13476 Ethylene vinyl alcohols, PVDC, water glass (Na ₂ SiO ₄ ), hydrophilic polyester (5-Na-sulfoisophthalsäurehaltiger PET / IPA polyester, as described for example in the EP-A-0 144 878 . US-A-4,252,885 or EP-A-0 296 620 ), Polyvinyl acetates, as described, for example in the WO 94/13481 , Polyurethanes, alkali metal or alkaline earth metal salts of C ₁₀ -C ₁₈ fatty acids, butadiene copolymers with acrylonitrile or methyl methacrylate, methacrylic acid or esters thereof.

The mentioned substances / compositions are as dilute solution, emulsion or dispersion, preferably as aqueous solution, emulsion or dispersion, on one or both surfaces of the film applied, and subsequently becomes the solvent volatilized. If the coatings are applied in-line before the transverse stretching, usually enough the temperature treatment in the transverse extension and subsequent heat fixation off to the solvent to evaporate and to dry the coating.

• (1) Isophthalsäure,
• (2) einer aliphatischen Dicarbonsäure mit der Formel HOOC(CH₂)_nCOOH, wobei n im Bereich von 1 bis 11 liegt,
• (3) einem Sulfomonomeren enthaltend eine Alkalimetallsulfonatgruppe an dem aromatischen Teil einer aromatischen Dicarbonsäure und
• (4) wenigstens einem aliphatischen oder cycloaliphatischen Alkylenglykol mit etwa 2 bis 11, bevorzugt 2 bis 8, besonders bevorzugt 2 bis 6 Kohlenstoffatomen hergestellt.

In a preferred embodiment of the invention, a copolyester coating is used to achieve better adhesion. The preferred coating copolyesters are obtained by polycondensation of

• (1) isophthalic acid,
• (2) an aliphatic dicarboxylic acid having the formula HOOC (CH ₂ ) _n COOH, where n is in the range of 1 to 11,
• (3) a sulfomonomer containing an alkali metal sulfonate group on the aromatic part of an aromatic dicarboxylic acid and
• (4) at least one aliphatic or cycloaliphatic alkylene glycol having about 2 to 11, preferably 2 to 8, more preferably 2 to 6 carbon atoms produced.

The total acid equivalents present should be present on a molar basis, essentially the total glycol equivalents correspond.

It has been shown that the proportionate shares the components (1), (2), (3) and (4) used in the preparation of the preferred Copolyester coatings are used, crucial for achieving a coated film with satisfactory adhesion. So should preferably z. B. isophthalic acid (component 1) to at least about 65 mole percent as the acid component to be present. Preferably, component (1) is pure isophthalic acid, which in an amount of about 70 to 95 mol% is present. For component (2) holds that every acid with the formula mentioned brings satisfactory results, wherein Adipic acid, azelaic acid, sebacic acid, malonic acid, succinic acid, glutaric acid and Mixtures of these acids to be favoured. The target amount within the specified Range is preferably 1 to 20 mol%, based on the acid components of the copolyester, when the component (3) is contained in the composition. The the component (3) forming the preferred copolyester coating Monomers should preferably be present in an amount of at least 5 mol% To be included in this system, so that the primer with water becomes dispersible. Most preferably, the amount of monomer the component (3) at about 6.5 to 12 mol%. The glycol component (4) is about stoichiometric Amount (based on the acid components present) present.

In a further preferred embodiment The invention provides an acrylate coating to achieve the better Liability used. The preferred acrylic copolymers are used essentially of at least 50% by weight of one or more polymerized acrylic and / or methacrylic monomer and 1 to 15% by weight a copolymerizable comonomer obtained in copolymerized form Condition under the influence of increased Temperature, optionally without the addition of a separate resinous vehicle, capable of forming intermolecular crosslinks.

The acrylic component of the primer copolymers is preferred in an amount of 50 to 99 wt .-% present and is preferred from an ester of methacrylic acid, in particular an alkyl ester whose alkyl group contains up to ten carbon atoms, such as z. As the methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tertiary Butyl, hexyl, 2-ethylhexyl, heptyl and n-octyl groups. acrylic copolymers derived from a lower alkyl acrylate (C1 to C4), especially ethyl acrylate, together with a lower alkyl methacrylate a particularly good adhesion between the polyester roll and on it applied reprographic coatings and matt coatings. Adhesion promoter copolymers are very particularly preferred Alkyl acrylate, e.g. As ethyl acrylate or butyl acrylate, together with an alkyl methacrylate, e.g. As methyl methacrylate, in particular to equal molar proportions and in a total amount of 70 to 95 Wt .-%, used. The acrylate comonomer of such acrylic / methacrylic combinations is preferably present in a proportion of 15 to 65 mol% and the methacrylate comonomer preferably in a proportion which is generally from 5 to 20 mol% is larger as the proportion of the acrylate comonomer. The methacrylate is preferred in a proportion of 35 to 85 mol% in the combination.

To increase the solvent resistance, suitable comonomers may optionally be used to form crosslinks such as. N-methylolacrylamide, N-methylolmethacrylamide and the corresponding ethers; Epoxy materials such. Glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether; Carboxyl group-containing monomers such as crotonic acid, itaconic acid or acrylic acid; anhydrides such as Maleic anhydride or itaconic anhydride; Hydroxyl-containing monomers such. Allyl alcohol and hydroxyethyl or hydroxypropyl acrylate or methacrylate; Amides such as As acrylamide, methacrylamide or maleic acid amide and isocyanates such. For example, vinyl isocyanate or allyl isocyanate. Of the above-mentioned crosslinking comonomers, N-methylolacrylamide and N-methylolmethacrylamide are preferred, primarily because copolymer chains containing one of these monomers, under the action of elevated temperatures, allow condensation with one another and thus formation of the desired intermolecular crosslinks are. The optionally desired solvent resistance of the preferred acrylate coating can also by the presence of a foreign crosslinking agent such. As a melamine or urea-formaldehyde condensation product can be achieved. If no solvent resistance is required, then crosslinking agents can be dispensed with.

The preferred acrylate coating can be applied to the film on one or both sides. However, it is also possible to provide only one side of the film with the coating according to the invention and to apply another coating to the opposite side. The coating formulation may contain known additives such as. As antistatic agents, wetting agents, surfactants, pH regulators, antioxidants, dyes, pigments, anti-blocking agents such. Colloidal SiO ₂ , etc. Normally, it is convenient to incorporate a surfactant to increase the ability of the aqueous coating to wet the polyester support sheet.

• 1. eine Mischung aus einem aromatischen Copolyester (I-1) mit einer in Wasser dispergierbaren funktionellen Gruppe und einem Polyvinylalkohol (II-1),
• 2. eine Mischung aus einem aromatischen Copolyester (I-2) mit einer in Wasser dispergierbaren funktionellen Gruppe und einem Polyglycerolpolyglycidylether (II-2) oder
• 3. eine Mischung aus einem wässrigen Polyurethan (I-3) und einem Polyvinylalkohol (II-3).

In a further preferred embodiment of the invention, a water-soluble or hydrophilic coating is used to achieve better adhesion with hydrophilic layers or printing inks. The preferred hydrophilic coating can be achieved in three ways:

• 1. a mixture of an aromatic copolyester (I-1) having a water-dispersible functional group and a polyvinyl alcohol (II-1),
• 2. a mixture of an aromatic copolyester (I-2) having a water-dispersible functional group and a polyglycerol polyglycidyl ether (II-2) or
• 3. a mixture of an aqueous polyurethane (I-3) and a polyvinyl alcohol (II-3).

The aromatic copolyesters (I-1 and I-2) are selected from aromatic dicarboxylic acids such as for example terephthalic acid, 2,6-naphthalene or isophthalic acid, optionally branched or fused aliphatic diols such as As ethylene glycol, diethylene glycol, 2-methylpropanol or 2,2-dimethylpropanol and an ester-forming compound, the carrying a water-dispersible functional group. examples for the functional groups are: hydroxyl, carboxyl, sulfonic acid or Phosphoric acid groups or their salts. Preference is given to sulfonic acid and carboxylic acid salts. As the polyvinyl alcohol component (II-1 and II-3), any polyvinyl alcohol be used, the water-soluble and can be prepared by normal polymerization techniques. As a general rule Such polyvinyl alcohols are obtained by saponification of polyvinyl acetates produced. The saponification degree should preferably be at least 70%, better, however, be 80 to 99.9%. As polyglycerol polyglycidyl ether (II-2) are reaction products of glycerol and epichlorohydrin used with molecular weights between about 250 and 1200 g / mol. The watery Polyurethane (I-3) is made of a polyol such as polyester with glycol end groups, polyoxyethylene glycol, polyoxypropylene glycol, Polyoxytetramethylene glycol or acrylic polyols, and a diisocyanate, such as xylene diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, Toluidine diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate and 1,5-naphthalene diisocyanate produced.

In a further preferred embodiment According to the invention, the adhesion-promoting layer consists of an amino-functional one Silane, which the film in addition steam-sterilized (a laminate of, for example, film, coating, Glue or coated metallic and ceramic layers does not delaminate) and above out for the direct extrusion coating with polymers receptive power.

As a general rule the aminofunctional silane is hydrolyzed in water and placed on a or more surfaces of the oriented polyester by conventional methods such as spraying or Roll coating applied. If the silane coating once is dried, the thus primed polyester is steam sterilizable and receptive for the direct extrusion with other polymers. The extrusion coating can be done with a conventional process.

In its broadest sense, the present invention is directed in this regard to an oriented polyester film having an adhesion-promoting layer that enables the film to be steam-sterilized and receptive to direct extrusion coating. The adhesion-promoting layer is described in its unhydrolyzed state by the following general formula: (R ¹ ) _a Si (R ² ) _b (R ³ ) _c .

The invention also encompasses a steam sterilisable laminate consisting of an oriented poly ester film, an adhesion-promoting layer and a directly extruded polymer.

silanes are water-soluble after hydrolysis or can be dispersed in water, with amino-functional silanes especially good water-soluble are. It has been found that aminosilanes have good adhesion to paints, Adhesives, primers and metallic and ceramic coatings too have after steam sterilization and also good adhesion from extrusion coated polymers to polyester films without one additional impart adhesion-promoting layer or corona treatment. Of the Blend of polyester film with aminosilane coating can be regenerated become.

Aminofunctional silanes that can be used for the purpose of this invention are described in their unhydrolyzed form by the following formula: (R ¹ ) _a Si (R ₂ ) _b (R ³ ) _c , wherein R ^{1 contains} at least one amino group; R ² is a hydrolyzable group selected from short chain alkoxy groups of 1 to 8 carbon atoms, an acetoxy group or halides; and R ³ is an unreactive, nonhydrolyzable group, either a short chain alkyl group of 1 to 8 carbon atoms or a phenyl group; with (a) greater than or equal to 1; (b) greater than or equal to 1; (c) greater than or equal to 0 and a + b + c = 4.

Examples of aminosilanes conforming to this formula are N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 4-aminobutyltriethoxysilane, 4-aminobutyldimethylmethoxysilane, and p-aminophenyltrimethoxysilane. The preferred silane is N-2- (aminoethyl) -3-aminopropyltrimethoxysilane having the following formula: H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ .

The hydrolyzed aminosilane can in principle to every possible Time to be applied in the production of the film, d. H. before or during of the stretching process, it can also be applied to the finished foil (eg) before be applied to the reel.

The Adhesive layer is made by the mixture of aminosilane preferably prepared with water in a range of 0.2 to 6 wt .-%. Optionally, a weak acid such as As acetic acid be added to promote hydrolysis. At least one of the hydrolyzable groups of the silane becomes a silanol group (SiOH) hydrolyzed. It is believed that the hydrolysis product the aminosilane has a partially hydrolyzed cyclic structure, where the amino group is probably ionic bonds to the silicon part of the molecule forms. Consequently, the term hydrolyzed refers to here is used, even on these partially hydrolyzed structures.

The coating according to the invention described above is described in detail in EP-B-0 359 017 (Pages 3 to 5), to which reference is expressly made at this point. This document also provides information about other specific combinations of such hydrolyzable aminosilanes.

The preferred copolyester, acrylate, silane and hydrophilic coatings may further contain other known additives such as e.g. As antistatic agents, wetting agents, surfactants, pH regulators, antioxidants, dyes, pigments, anti-blocking agents such. As colloidal SiO ₂ , etc.

The inventive film is characterized in particular by excellent optical properties, d. H. a low gloss and low transparency, a very good one Handling and by a very good processing behavior.

Besides in the production of the film, it is ensured that which is obtained in the production of the film in larger quantities than Regenerate in an amount in the range of about 20 to 60 wt .-%, based on the total weight of the film, re-fed to the extrusion can, without losing the physical properties of the film are significantly negatively affected, especially not their optical Appearance.

The Film is therefore very well suited for use in the flexible Packaging, especially where its excellent optical Properties and their good processability come to fruition such as B. when used on high-speed packaging machines.

The The table below (Table 1) summarizes the main invention and preferred film properties together again:

DIN

= Deutsches Institut für Normung

ASTM

= American Society for Testing and Materials

To characterize the raw materials and the films, the following measuring methods were used:

DIN

= German Institute for Standardization

ASTM

= American Society for Testing and Materials

SV value (standard viscosity)

The standard viscosity SV (DCE) is measured, based on DIN 53726, at 25 ° C. in dichloroacetic acid. The intrinsic viscosity (IV) is calculated from the standard viscosity as follows. IV [η] = 6.907 x 10 -4 SV (DCE) + 0.063096 [dl / g]

shine

Of the Gloss is determined according to DIN 67 530. The reflector value is measured as an optical parameter for the surface of a Foil. Based on the standards ASTM-D 523-78 and ISO 2813, the Beam angle with 20 ° or 60 ° set. A light beam hits below the set angle of incidence the flat test surface and is reflected or scattered by this. The on the photoelectronic receiver striking light rays are called proportional electric Size displayed. The measured value is dimensionless and must match the angle of incidence be specified.

whiteness

The degree of whiteness is determined by Berger, with more than 20 layers of film usually being stacked on top of each other. The whiteness is determined with the aid of the ELREPHO electric remission photometer from Zeiss, Oberkochem (DE), standard illuminant C, 2 ° normal observer. The whiteness WG is called WG = RY + 3RZ - 3RX where RX, RY, RZ are respective reflection factors when using an X, Y, Z color measurement filter. As a white standard, a compact of barium sulfate (DIN 5033, Part 9) is used. A detailed description is z. B. Hansl Loos, color measurement, publishing profession and school, Itzehoe (1989) described.

roughness

The roughness R _{a of} the film is determined according to DIN 4768 at a cut-off of 0.25 mm. It is not measured on a glass plate, but in the ring. In the ring method, the foil is clamped in a ring, so that neither of the two surfaces touches a third surface (eg glass).

Measurement of the mean diameter d ₅₀ (mean particle diameter)

The determination of the mean diameter d ₅₀ is carried out on a Master Sizer Malvern Instruments, GB, by means of laser scanning [other measuring devices are z. B. Horiba LA 500 (Horiba Europe GmbH, DE) or Helos (Sympathec, DE), which use the same measuring principle)]. The samples are then placed in a cuvette with water and then placed in the meter. The dispersion is scanned by laser and the particle size distribution is determined from the signal by comparison with a calibration curve. The particle size distribution is characterized by two parameters, the median value d ₅₀ (= positional measure for the mean value) and the scattering ratio, the so-called SPAN98 (= measure of the scattering of the particle diameter). The measuring process is automatic and includes the mathematical determination of the d ₅₀ value. By definition, the d ₅₀ value is determined from the (relative) cumulative curve of the particle size distribution: the point of intersection of the 50% ordinate value with the cumulative curve gives the desired d ₅₀ value on the abscissa axis [also called median, cf. 1 , Φ (d) = (relative) sum of particles].

Measurement of SPAN98

The determination of the scattering measure, the SPAN98, is carried out with the same measuring instrument as described above in the determination of the mean diameter d ₅₀ . The SPAN98 is defined as follows:

The determination of d ₉₈ and d ₁₀ again becomes the (relative) cumulative curve of the particle size distribution based on. The point of intersection of the 98% ordinate value with the cumulative curve immediately gives the desired d ₉₈ value on the abscissa axis, and the point of intersection of the 10% ordinate value of the cumulative curve with the curve gives the desired d ₁₀ value on the abscissa axis (cf. 2 ). The transparency is measured using a Haze TC from Pausch Messtechnik, DE, or Hazegard-plus from Byk-Gardner, USA, according to ASTM D 1003-61.

topography

The Topography of the surface is using a white light interferometry microscope the company Veeco, type Wyko NT3300. Measured is an area of 0.92 mm × 1.21 mm (480 × 736 Pixels) at 5.1x magnification. For measurement, the sample is clamped in a ring (diameter 40 mm) The measurement is performed in VSI mode (phase shifting interferometry). The measuring length in z-direction is on 20 microns established. A possible ripple of the pattern is filtered out.

To analyze the surveys, the so-called multi-region analysis is used. Here, the measurement surface is examined for contiguous regions that are higher than 1.5 μm. However, only regions with a size of at least 5 pixels are considered. An example is in 3 shown.

Contact angle with water

The polarity the surface is determined by a contact angle measurement of distilled water. The Measurement takes place at 23 ° C and 50% r. F. held. By means of a metering syringe is a 1 to 2 mm wide drop of distilled water applied to the film surface. Because the measurement is due to heat the lighting (evaporation), charging or spreading behavior is time-dependent, the needle remains in the drop, so that the drop during the Measurement carefully enlarged and then Immediately read the contact angle using a goniometer eyepiece becomes (measurement of the advancing angle). From 5 measurements becomes the Mean value formed.

in the The invention will be explained in more detail below with reference to examples.

example 1

polyethylene terephthalate and polyethylene terephthalate containing titanium dioxide as a white pigment were dried and fed to the base layer extruder (B). Also were polyethylene terephthalate and polyethylene terephthalate containing Titanium dioxide as white pigment and polyethylene terephthalate containing the further pigment and the extruder for the cover layer (A) supplied.

Then, by coextrusion and subsequent stepwise orientation in the longitudinal and transverse directions, a white two-layer film with AB structure and a total thickness of 50 microns was prepared. The thickness of the cover layer was 2 μm. Base layer (B): 86% by weight Polyethylene terephthalate with an SV value of 800 14% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800 Covering layer (A), mixture of: 14% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800 70% by weight Polyester raw material, consisting of 95 wt .-% (copolyester of 78 mol% terephthalic acid, 22 mol% isophthalic acid and 100 mol% ethylene glycol) and 5.0 wt .-% silica particles (Sylysia 430 from Fuji, JP) with a d ₅₀ value of 3.4 μm and SPAN98 of 1.6 and an SV value of 800 16% by weight Polyester raw material, consisting of 95 wt .-% (polyester from 99 mol% terephthalic acid, 1 mol% isophthalic acid and 100 mol% ethylene glycol) and 5 wt .-% silica particles (Sylysia 430 from. Fuji, JP) with a d ₅₀ value of 3.4 μm and SPAN98 of 1.6 and an SV value of 800

The production conditions in the individual process steps were: extrusion temperatures A-layer: 280 ° C B layer: 280 ° C C layer: 280 ° C Temperature of the take-off roll 20 ° C longitudinal stretching temperature 70-120 ° C Longitudinal stretching ratio 3.2 transverse stretching temperature 80-135 ° C Transverse stretching ratio 3.8 fixation temperature 230 ° C duration 3 s

It was a film with a high degree of matt, with very good winding behavior, a very good winding quality and a very good processing behavior.

Example 1a

A film was produced as described in Example 1, but after fixing, the film was subjected to a corona treatment (2 kW / m ² ). It was a film with a high degree of matt, with very good winding behavior, a very good winding quality and a very good processing behavior. The cover layer (A) of the film had the desired improved adhesion, the contact angle to water was 63.7 °.

Example 1b

The film was made as in Example 1a, but without corona treatment after biaxial stretching. A 4.5% solids by weight solids consisting of a copolymer of 60% by weight of methyl methacrylate, 35% by weight of ethyl acrylate, and 5% by weight of N-methylolacrylamide and a surfactant was used as a primer coating according to the following procedure applied to the A-layer of the polyester film:
The elongated film was corona treated (8 kW / m ² ) and then coated by reverse gravure coating on the A layer with the above-described latex.

The biaxially stretched film was heat-set at 230 ° C. The dry weight of the coating was about 0.035 g / m ² at a coating thickness of about 40 nm.

The desirable and properties of the invention of the film were as in Example 1a. The contact angle to water the A-layer surface was 63.9 °. The film was tested for its reprographic adhesion and resulted a good adhesion.

Example 1c

The film was produced as in Example 1b. An aqueous dispersion containing 6% by weight copolyester consisting of 95 mole% isophthalate, 5 mole% Na-5 sulfoisophthalate and 100 mole% ethylene glycol and 0.56 weight% colloidal SiO ₂ was prepared by the following procedure applied as a coating on the polyester film:
The elongated film was coated by reverse gravure coating on the A layer with the copolyester dispersion described above.

The biaxially stretched film was heat-set at 230 ° C. The dry weight of the coating was about 0.030 g / m ² at a coating thickness of about 35 nm.

Of the Contact angle to water was 57 °.

Two Samples of the one-side coated film thus prepared were placed in a vacuum lab coater, in such a way that at one coated and the other uncoated Side was metallized. The vacuum chamber was down to under 10 Torr evacuated, and from a tungsten filament about 500 Å of aluminum was evolved on both the uncoated side and the coated sample evaporated.

Within every 30 seconds after removal from the vacuum chamber, each sample was tested for "metal abrasion". To this The purpose was on each sample tested with a cotton fleece with the same number of strokes and about the same pressure slightly over the metal surface rubbed. The "abrasion behavior" of the coated Side of the film was rated as good. The "abrasion behavior" of the uncoated Page was rated as bad.

Example 1d

The film was made as in Example 1a, but without corona treatment after biaxial stretching. A 7% by weight solids aqueous dispersion consisting of 50% by weight of aromatic copolyester (copolyester containing 90 mole% terephthalate, 10 mole% 5-sodiosulfoisophthalate, 80 mole% ethylene glycol and 20 mole% diethylene glycol), 45% by weight of water-dispersible polymer (polyvinyl alcohol having a saponification degree of 88 mol% and a degree of polymerization of 1,700) and 5% by weight of inert particles (colloidal SiO ₂ having a particle diameter of 0.05 μm) became as follows Method applied as a coating on a polyester film:
The longitudinally stretched film was coated by reverse gravure coating with the copolyester dispersion described above on topcoat (A). The dry weight of the coating was about 0.040 g / m ² at a coating thickness of about 0.05 μm.

The contact angle to water was 49.7 °:
To evaluate the coupling effect of the coating, an aqueous polyvinyl acetal solution (S-Lec KX-1, manufactured by Sekisui Chemical Co., Ltd., hereinafter referred to as KX-1) was applied to the coated film and dried. The coating solution had a concentration of 8% by weight and was applied with a Baker type applicator with a layer thickness of 127 μm. The coated film was immediately placed in an oven for drying at 100 ° C for 4 minutes. A black square (area: 12 × 12 cm) was printed on the surface of the dried KX-1 coating with an ink jet printer (BJC-600J, Canon Inc.) and incubated for 12 h at 23 ° C and 50%. relative humidity dried in air. An adhesive tape (Cello-tage, Nichiban Inc., width: 18 mm) was glued to the printed area and peeled off quickly. The degree of the printed surface separated with the adhesive tape was visually determined. The coated film showed good adhesion properties.

Example 2

In comparison with Example 1, an ABA film was now produced and the composition of the outer layers (A) changed. The total thickness of the film was 60 μm. The thickness of the outer layers was 3 μm. All other parameters were retained. 14% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800 30% by weight Polyester raw material, consisting of 95 wt .-% (copolyester from 78 mol% terephthalic acid, 22 mol% isophthalic acid and 100 mol% ethylene glycol) and 5 wt .-% silica particles (Sylysia 430 from. Fuji, JP) with a d ₅₀ value of 3.4 μm and SPAN98 of 1.6 and an SV value of 800 36% by weight Polyester raw material, consisting of 95 wt .-% (polyester from 99 mol% terephthalic acid, 1 mol% isophthalic acid and 100 mol% ethylene glycol) and 5 wt .-% silica particles (Sylysia 430 from. Fuji, JP) with a d ₅₀ value of 3.4 μm and SPAN98 of 1.6 and an SV value of 800 20% by weight Polyethylene terephthalate with an SV value of 800

Example 3

Compared to Example 1, an ABA film was now produced and the composition of the outer layers (A) and the base (B) changed. The total thickness of the film was 50 μm. The thickness of the cover layers was 2 μm. All other parameters were retained. Base layer (B): 90% by weight Polyethylene terephthalate with an SV value of 800 10% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800 Covering layer (A), mixture of: 10% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800 50% by weight Polyester raw material, consisting of 95 wt .-% (copolyester from 78 mol% terephthalic acid, 22 mol% isophthalic acid and 100 mol% ethylene glycol) and 5 wt .-% silica particles (Sylysia 430 from. Fuji, JP) with a d ₅₀ value of 3.4 μm and SPAN98 of 1.6 and an SV value of 800 40% by weight Polyester raw material, consisting of 95 wt .-% (polyester from 99 mol% terephthalic acid, 1 mol% isophthalic acid and 100 mol% ethylene glycol) and 5 wt .-% silica particles (Sylysia 430 from. Fuji, JP) with a d ₅₀ value of 3.4 μm and SPAN98 of 1.6 and an SV value of 800

Example 4

Compared to Example 1, an ABC film has now been produced and the composition of the outer layers (A) and (C) and the base layer (B) changed. All other parameters (manufacturing conditions) have been retained. The total thickness of the film was 25 μm. The thickness of the cover layers was 1.5 μm. Cover layer (A) 20% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800 80% by weight Polyester raw material, consisting of 95 wt .-% (copolyester of 82 mol% terephthalic acid, 18 mol% isophthalic acid and 100 mol% ethylene glycol) and 5 wt .-% silica particles (Sylysia 430 from. Fuji, JP) with a d ₅₀ value of 3.4 μm and SPAN98 of 1.6 and an SV value of 800 Base layer (B) 80% by weight Polyethylene terephthalate with an SV value of 800 20% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800 Cover layer (C) 92% by weight Polyethylene terephthalate with an SV value of 800 8% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800

Comparative Example 1

Compared to Example 1, only the composition of the outer layers (A) has been changed. The other particles in the cover layers were omitted. All other parameters were retained. Covering layer (A), mixture of: 86% by weight Polyethylene terephthalate with an SV value of 800 14% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800

The Slide no longer had the desired matte appearance. The shine was too high and the roughness too low.

Comparative Example 2

Example 4 was made EP-A-1 442 875 reworked. The transparent film had the required roughness and gloss, but not the required transparency and whiteness.

Comparative Example 3

Compared to Example 1, only the composition of the outer layers (A) has been changed. The other particles in the cover layers were omitted. All other parameters were retained. Covering layer (A), mixture of: 16% by weight Polyethylene terephthalate with an SV value of 800 14% by weight Masterbatch from Sukano (Schindellegi, CH) with 50 wt .-% rutile titanium dioxide (average particle diameter titanium dioxide about 0.3 microns) and 50 wt .-% polyethylene terephthalate with an SV value of 800 70% by weight Masterbatch of 95 wt .-% polyethylene terephthalate and 5 wt .-% silica particles (Sylysia 430 from Fuji, JP) with a d ₅₀ value of 3.4 microns and an SV value of 800

The Slide no longer had the desired matte appearance. The shine was too high and the roughness too low.

The Results of Examples / Comparative Examples are summarized in Table 2.

Claims (24)

Polyester film, which has at least one white base layer (B) and at least one matte outer layer (A), characterized in that a. the base layer (B) contains white pigment in a concentration of 3 to 15% by weight (based on the weight of the base layer (B)), b. the cover layer (A) contains white pigment in a concentration of 2 to 15% by weight (based on the weight of the cover layer (A)) and c. the cover layer (A) contains further particles other than the white pigment which have an average particle diameter d ₅₀ of 2 to 10 μm, and d. the cover layer (A) is constructed of a polyester having from 4 to 30 mol% of isophthalic acid units (based on the total amount of acid of the polyester in this layer). Polyester film according to claim 1, characterized that the white pigment selected is from the group: titanium dioxide, barium sulfate, zinc sulfide, zinc oxide and mixtures thereof. Polyester film according to claim 2, characterized in that the white pigment is TiO ₂ . Polyester film according to claim 3, characterized that the grain size of titanium dioxide between 0.05 and 0.5 microns lies. Polyester film according to claim 3 or 4, characterized that the titanium dioxide is rutile type. Polyester film according to one of claims 1 to 5, characterized in that the particles other than white pigment selected are made of calcium carbonate, amorphous silica, talc, magnesium carbonate, Barium carbonate, calcium sulfate, lithium phosphate, calcium phosphate, Magnesium phosphate, alumina, lithium fluoride, calcium, barium, Zinc or manganese salts the dicarboxylic acids used, Kaolin, crosslinked polymer particles and mixtures of these particles. Polyester film according to one of claims 1 to 6, characterized in that the particles other than white pigment are synthetically produced SiO ₂ particles (in colloidal form). Polyester film according to one of claims 1 to 7, characterized in that the roughness of the matte side of Film is in the range of 150 to 1000 nm. Polyester film according to one of claims 1 to 8, characterized in that the surface of the matte side of the film> 100 to <1500 surveys per mm ² , which are greater than 1.5 microns. Polyester film according to one of claims 1 to 9, characterized in that the film of three layers, the Base layer (B) and applied on both sides of this base layer Cover layers (A) and (C), wherein the outer layers (A) and (C) are the same or different. Polyester film according to one of claims 1 to 10, characterized in that it has a brightness greater than Berger of 75 has. Polyester film according to one of claims 1 to 11, characterized in that the cover layer (A) has a gloss (60 °) of less than 50. Polyester film according to one of claims 1 to 12, characterized in that it has a transparency of less than 50%. Polyester film according to one of claims 1 to 13, characterized in that at least one surface of the Film is functionalized by a treatment. Polyester film according to claim 14, characterized that the treatment is a corona treatment. Polyester film according to claim 13 or 14, characterized characterized in that the treatment is a coating of the film is. Polyester film according to claim 16, characterized that the coating is an acrylate coating. Polyester film according to claim 16, characterized that the coating has a coating with an amino-functional Silane is. Polyester film according to claim 16, characterized the coating is a hydrophilic coating. Polyester film according to claim 16, characterized the coating is a copolyester coating. A process for producing a polyester film according to claim 1, comprising the steps of: a) producing a multilayer film comprising at least a base layer (B) and a cover layer (A) by coextrusion and molding the melts into flat melt films; b) biaxially stretching the film; and c Heat-setting the stretched film, characterized in that the base layer (B) contains white pigment in a concentration of 3 to 15 wt .-% (based on the weight of the base layer (B)), the top layer (A) white pigment in a concentration of 2 to 15 wt .-% contains (based on the weight of the outer layer (A)) and the outer layer (A) further, different from the white pigment containing particles having a mean particle diameter d ₅₀ from 2 to 10 microns, and the cover layer (A) is constructed of a polyester having 4 to 30 mol% of isophthalic acid units (based on the total amount of acid of the polyester in this layer). Use of a polyester film according to one of claims 1 to 20 as a flexible packaging film, in particular for food and beverage. Use of a polyester film according to claim 22 as a cover foil for Food containers, in particular yogurt cups. Use of a polyester film according to claim 22 or 23, characterized in that the packaging operation on fast-running packaging machines.